<script id="shadow-shader-vs" type="x-shader/x-vertex">
  precision mediump float;
  
  attribute vec3 inPos;
  
  varying vec4 vPosPrj;
  
  uniform mat4 u_projectionMat44;
  uniform mat4 u_viewMat44;
  uniform mat4 u_modelMat44;
  
  void main()
  {
      vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
      vec4 viewPos  = u_viewMat44 * modelPos;
      vPosPrj       = u_projectionMat44 * viewPos;
      gl_Position   = vPosPrj;
  }
</script>

<script id="shadow-shader-fs" type="x-shader/x-fragment">
    precision mediump float;
    
    varying vec4 vPosPrj;

    uniform vec2 u_depthRange;

    vec3 PackDepth( in float depth )
    {
        float depthVal = depth * (256.0*256.0*256.0 - 1.0) / (256.0*256.0*256.0);
        vec4 encode = fract( depthVal * vec4(1.0, 256.0, 256.0*256.0, 256.0*256.0*256.0) );
        return encode.xyz - encode.yzw / 256.0 + 1.0/512.0;
    }
    
    void main()
    {
        float ndc_depth = vPosPrj.z / vPosPrj.w;
        float nearZ     = u_depthRange.x;
        float farZ      = u_depthRange.y;
        float depth     = ndc_depth * 0.5 + 0.5;
        gl_FragColor    = vec4( PackDepth( depth ).xyz, 1.0 );
    }
</script>

<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;

attribute vec3 inPos;
attribute vec3 inNV;
attribute vec3 inCol;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
varying vec4 lightPrj;

uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;
uniform mat4 u_lightProjectionMat44;
uniform mat4 u_lightViewMat44;

void main()
{
    vec3 modelNV  = mat3( u_modelMat44 ) * normalize( inNV );
    vertNV        = mat3( u_viewMat44 ) * modelNV;
    vertCol       = inCol;
    vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
    vec4 lightPos = u_lightViewMat44 * modelPos;
    vec4 viewPos  = u_viewMat44 * modelPos;
    lightPrj      = u_lightProjectionMat44 * lightPos;
    vertPos       = viewPos.xyz / viewPos.w;
    gl_Position   = u_projectionMat44 * viewPos;
}
</script>
  
<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
varying vec4 lightPrj;

uniform sampler2D u_depthSampler;
uniform vec3      u_lightDir;
uniform float     u_ambient;
uniform float     u_diffuse;
uniform float     u_specular;
uniform float     u_shininess;

float UnpackDepth( in vec3 pack )
{
  float depth = dot( pack, 1.0 / vec3(1.0, 256.0, 256.0*256.0) );
  return depth * (256.0*256.0*256.0) / (256.0*256.0*256.0 - 1.0);
}

float Depth( in sampler2D depthSampler, in vec2 texC )
{
  vec3 depthVal = texture2D( depthSampler, texC.st ).xyz;  
  return UnpackDepth( depthVal.rgb );
}

void main()
{
    vec3  ndc_light  = lightPrj.xyz / lightPrj.w;
    vec2  lightTexC  = ndc_light.xy * 0.5 + 0.5;
    float lightDepth = ndc_light.z * 0.5 + 0.5;
    float testDepth  = Depth( u_depthSampler, lightTexC );
    float shadow     = step( lightDepth-0.01, testDepth ) + step( testDepth, 0.0 );
    vec3  color      = vertCol;
    vec3  lightCol   = u_ambient * color;
    vec3  normalV    = normalize( vertNV );
    vec3  lightV     = normalize( -u_lightDir );
    float NdotL      = max( 0.0, dot( normalV, lightV ) );
    lightCol        += shadow * NdotL * u_diffuse * color;
    vec3  eyeV       = normalize( -vertPos );
    vec3  halfV      = normalize( eyeV + lightV );
    float NdotH      = max( 0.0, dot( normalV, halfV ) );
    float kSpecular  = ( u_shininess + 2.0 ) * pow( NdotH, u_shininess ) / ( 2.0 * 3.14159265 );
    lightCol        += shadow * kSpecular * u_specular * color;
    gl_FragColor     = vec4( lightCol.rgb, 1.0 );
}
</script>

<style>
html,body { margin: 0; overflow: hidden; }
#gui { position : absolute; top : 0; left : 0; font-size : large; }
#ref-link { position : absolute; bottom : 0; left : 0; font-size : large; }  
</style>
    
</style>

<body>

<div><form id="gui" name="inputs"><table>
    <tr> <td> <font color= #CCF>ambient</font> </td> 
            <td> <input type="range" id="ambient" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color= #CCF>diffuse</font> </td> 
            <td> <input type="range" id="diffuse" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color= #CCF>specular</font> </td> 
            <td> <input type="range" id="specular" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color= #CCF>shininess</font> </td> 
            <td> <input type="range" id="shininess" min="0" max="100" value="0"/></td> </tr>
</table></form></div>

<div id="ref-link">
<a href="https://stackoverflow.com/questions/46122584/opengl-es3-shadow-map-problems/46123519#46123519"> 
OpenGL ES3 Shadow map problems
</a>
</div>

<!--canvas id="scene-canvas" style="border: none;" width="100%" height="100%"></canvas-->
<canvas id="scene-canvas" style="border: none;" width="512" height="512"></canvas>

<script type="text/javascript">

(function loadscene() {

var sliderScale = 100.0
var gl;
var progShadow;
var progDraw;
var shadowFB;
var bufTorus;
var bufGround;
var canvas;
var vp_size;
var fb_size;
var camera;

function render(deltaMS){

var ambient = document.getElementById( "ambient" ).value / sliderScale;
var diffuse = document.getElementById( "diffuse" ).value / sliderScale;
var specular = document.getElementById( "specular" ).value / sliderScale;
var shininess = document.getElementById( "shininess" ).value;

var lightPos = [-3.0, 0.0, 2.0];
var lightAnimationMat = RotateAxis( IdentM44(), CalcAng( deltaMS, 20.0 ), 2 );
lightPos = Transform( lightPos, lightAnimationMat );
var lightDir = [ -lightPos[0], -lightPos[1], -lightPos[2] ];
var light  = new Camera( lightPos, [0, 0, 0], [0, 0, 1], 110, [ 5.0, 5.0 ], -20.0, 20.0 );

camera.Update( vp_size );

var lightPrjMat = light.Ortho();
var lightViewMat = light.LookAt();
var prjMat = camera.Perspective();
var viewMat = camera.LookAt();
var modelMat = IdentM44();
modelMat = camera.Track();
//modelMat = RotateAxis( modelMat, CalcAng( deltaMS, 13.0 ), 0 );
//modelMat = RotateAxis( modelMat, CalcAng( deltaMS, 17.0 ), 1 );
groundModelMat = IdentM44();
var viewLightDir = TransformVec( lightDir, viewMat );
    
gl.viewport( 0, 0, fb_size[0], fb_size[1] );
gl.enable( gl.DEPTH_TEST );

shadowFB.Bind( true );
ShProg.Use( progShadow );
ShProg.SetM44( progShadow, "u_projectionMat44", lightPrjMat );
ShProg.SetM44( progShadow, "u_viewMat44", lightViewMat );
ShProg.SetM44( progShadow, "u_modelMat44", modelMat );
ShProg.SetF2( progShadow, "u_depthRange", [light.near, light.far] );

VertexBuffer.Draw( bufTorus, [0] );

gl.viewport( 0, 0, vp_size[0], vp_size[1] );
shadowFB.Release( true );
shadowFB.BindTexture( 1 );
ShProg.Use( progDraw );
ShProg.SetM44( progDraw, "u_projectionMat44", prjMat );
ShProg.SetM44( progDraw, "u_viewMat44", viewMat );
ShProg.SetM44( progDraw, "u_lightProjectionMat44", lightPrjMat );
ShProg.SetM44( progDraw, "u_lightViewMat44", lightViewMat );
ShProg.SetM44( progDraw, "u_modelMat44", modelMat );
ShProg.SetI1( progDraw, "u_depthSampler", 1 );
ShProg.SetF3( progDraw, "u_lightDir", viewLightDir )
ShProg.SetF1( progDraw, "u_ambient", ambient )
ShProg.SetF1( progDraw, "u_diffuse", diffuse )
ShProg.SetF1( progDraw, "u_specular", specular )
ShProg.SetF1( progDraw, "u_shininess", shininess )

VertexBuffer.Draw( bufTorus );
ShProg.SetM44( progDraw, "u_modelMat44", groundModelMat );
VertexBuffer.Draw( bufGround );

requestAnimationFrame(render);
}

function nearestPow2( aSize ){
  return Math.pow( 2, Math.round( Math.log( aSize ) / Math.log( 2 ) ) ); 
}

function resize() {
    //vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
    vp_size = [window.innerWidth, window.innerHeight];
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];

    var size = Math.max(256, Math.max(vp_size[0], vp_size[1]));
    size = nearestPow2(size/2);
    fb_size = [size, size]
    shadowFB = FrameBuffer.Create( fb_size ); 
}

function initScene() {

document.getElementById( "ambient" ).value = 0.2 * sliderScale;
document.getElementById( "diffuse" ).value = 0.7 * sliderScale;
document.getElementById( "specular" ).value = 0.5 * sliderScale;
document.getElementById( "shininess" ).value = 8.0;

canvas = document.getElementById( "scene-canvas");
vp_size = [canvas.width, canvas.height];
gl = canvas.getContext( "experimental-webgl" );
if ( !gl )
  return;

progShadow = ShProg.Create( 
[ { source : "shadow-shader-vs", stage : gl.VERTEX_SHADER },
{ source : "shadow-shader-fs", stage : gl.FRAGMENT_SHADER }
] );
if (!progShadow.progObj)
    return null;
progShadow.inPos = ShProg.AttrI( progShadow, "inPos" );

progDraw = ShProg.Create( 
  [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
    { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
  ] );
if (!progDraw.progObj)
    return null;
progDraw.inPos = ShProg.AttrI( progDraw, "inPos" );
progDraw.inNV  = ShProg.AttrI( progDraw, "inNV" );
progDraw.inCol = ShProg.AttrI( progDraw, "inCol" );

// create torus
var circum_size = 32, tube_size = 32;
var rad_circum = 1.0;
var rad_tube = 0.5;
var torus_pts = [];
var torus_nv = [];
var torus_col = [];
var torus_inx = [];
var col = [1, 0.5, 0.0];
for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
    var center = [
        Math.cos(2 * Math.PI * i_c / circum_size),
        Math.sin(2 * Math.PI * i_c / circum_size) ]
    for ( var i_t = 0; i_t < tube_size; ++ i_t ) {
        var tubeX = Math.cos(2 * Math.PI * i_t / tube_size)
        var tubeY = Math.sin(2 * Math.PI * i_t / tube_size)
        var pt = [
            center[0] * ( rad_circum + tubeX * rad_tube ),
            center[1] * ( rad_circum + tubeX * rad_tube ),
            tubeY * rad_tube ]
        var nv = [ pt[0] - center[0] * rad_tube, pt[1] - center[1] * rad_tube, tubeY * rad_tube ]
        torus_pts.push( pt[0], pt[1], pt[2] );
        torus_nv.push( nv[0], nv[1], nv[2] );
        torus_col.push( col[0], col[1], col[2] );
        var i_cn = (i_c+1) % circum_size
        var i_tn = (i_t+1) % tube_size
        var i_c0 = i_c * tube_size; 
        var i_c1 = i_cn * tube_size; 
        torus_inx.push( i_c0+i_t, i_c0+i_tn, i_c1+i_t, i_c0+i_tn, i_c1+i_t, i_c1+i_tn )
    }
}
bufTorus = VertexBuffer.Create(
  [ { data : torus_pts, attrSize : 3, attrLoc : progDraw.inPos },
    { data : torus_nv,  attrSize : 3, attrLoc : progDraw.inNV },
    { data : torus_col, attrSize : 3, attrLoc : progDraw.inCol } ],
    torus_inx
);

var g_l = 8.0;
var g_h = -2.5;
var g_c = [ 0.8, 0.6, 0.8 ];
bufGround = VertexBuffer.Create( 
    [ { data : [ -g_l, -g_l, g_h, g_l, -g_l, g_h, g_l, g_l, g_h, -g_l, g_l, g_h ], attrSize : 3, attrLoc : progDraw.inPos },
      { data : [ 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0 ], attrSize : 3, attrLoc : progDraw.inNV },
      { data : [ g_c[0], g_c[1], g_c[2], g_c[0], g_c[1], g_c[2], g_c[0], g_c[1], g_c[2], g_c[0], g_c[1], g_c[2] ], attrSize : 3, attrLoc : progDraw.inCol } ],
    [ 0, 1, 2, 0, 2, 3 ]
);

window.onresize = resize;
resize();
camera = new Camera( [0, 2.5, 2], [0, 0, 0], [0, 0, 1], 110, [vp_size[0], vp_size[1]], 0.5, 100.0 );
requestAnimationFrame(render);
}

function Fract( val ) { 
    return val - Math.trunc( val );
}
function CalcAng( deltaTime, intervall ) {
    return Fract( deltaTime / (1000*intervall) ) * 2.0 * Math.PI;
}

function IdentM44() { return [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1]; }

function RotateAxis(matA, angRad, axis) {
    var aMap = [ [1, 2], [2, 0], [0, 1] ];
    var a0 = aMap[axis][0], a1 = aMap[axis][1]; 
    var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
    var matB = matA.slice(0);
    for ( var i = 0; i < 3; ++ i ) {
        matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
        matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
    }
    return matB;
}

function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
    var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
    return [ v[0] / len, v[1] / len, v[2] / len ];
}

Transform = function(vec, mat) {
    return [
        vec[0] * mat[0*4+0] + vec[1] * mat[1*4+0] + vec[2] * mat[2*4+0] + mat[3*4+0],
        vec[0] * mat[0*4+1] + vec[1] * mat[1*4+1] + vec[2] * mat[2*4+1] + mat[3*4+1],
        vec[0] * mat[0*4+2] + vec[1] * mat[1*4+2] + vec[2] * mat[2*4+2] + mat[3*4+2],
        vec[0] * mat[0*4+3] + vec[1] * mat[1*4+3] + vec[2] * mat[2*4+3] + mat[3*4+3] ]
    if ( h[3] == 0.0 )
        return [0, 0, 0]
    return [ h[0]/h[3], h[1]/h[3], h[2]/h[3] ];
}

TransformVec = function(vec, mat) {
   return [
        vec[0] * mat[0*4+0] + vec[1] * mat[1*4+0] + vec[2] * mat[2*4+0],
        vec[0] * mat[0*4+1] + vec[1] * mat[1*4+1] + vec[2] * mat[2*4+1],
        vec[0] * mat[0*4+2] + vec[1] * mat[1*4+2] + vec[2] * mat[2*4+2] ]
}

function Rotate(matA, angRad, axis) {
    var s = Math.sin(angRad), c = Math.cos(angRad);
    var x = axis[0], y = axis[1], z = axis[2]; 
    matB = [
        x*x*(1-c)+c,   x*y*(1-c)-z*s, x*z*(1-c)+y*s, 0,
        y*x*(1-c)+z*s, y*y*(1-c)+c,   y*z*(1-c)-x*s, 0,
        z*x*(1-c)-y*s, z*y*(1-c)+x*s, z*z*(1-c)+c,   0,
        0,             0,             0,             1 ];
    return Multiply(matA, matB);
}  

function Multiply(matA, matB) {
    matC = IdentM44();
    for (var i0=0; i0<4; ++i0 )
        for (var i1=0; i1<4; ++i1 )
            matC[i0*4+i1] = matB[i0*4+0] * matA[0*4+i1] + matB[i0*4+1] * matA[1*4+i1] + matB[i0*4+2] * matA[2*4+i1] + matB[i0*4+3] * matA[3*4+i1]  
    return matC;
}

Camera = function( pos, target, up, fov_y, vp, near, far ) {
    this.Time = function() { return Date.now(); }
    this.pos = pos;
    this.target = target;
    this.up = up;
    this.fov_y = fov_y;
    this.vp = vp;
    this.near = near;
    this.far = far;
    this.orbit_mat = this.current_orbit_mat = this.model_mat = this.current_model_mat = IdentM44();
    this.mouse_drag = this.auto_spin = false;
    this.auto_rotate = true;
    this.mouse_start = [0, 0];
    this.mouse_drag_axis = [0, 0, 0];
    this.mouse_drag_angle = 0;
    this.mouse_drag_time = 0;
    this.drag_start_T = this.rotate_start_T = this.Time();
    this.Ortho = function() {
        var fn = this.far + this.near;
        var f_n = this.far - this.near;
        var w = this.vp[0];
        var h = this.vp[1];
        return [
            2/w, 0,   0,       0,
            0,   2/h, 0,       0,
            0,   0,   -2/f_n,  0,
            0,   0,   -fn/f_n, 1 ];
    };  
    this.Perspective = function() {
        var n = this.near;
        var f = this.far;
        var fn = f + n;
        var f_n = f - n;
        var r = this.vp[0] / this.vp[1];
        var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
        return [
            t/r, 0, 0,          0,
            0,   t, 0,          0,
            0,   0, -fn/f_n,   -1,
            0,   0, -2*f*n/f_n, 0 ];
    }; 
    this.LookAt = function() {
        var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
        var mx = Normalize( Cross( this.up, mz ) );
        var my = Normalize( Cross( mz, mx ) );
        var tx = Dot( mx, this.pos );
        var ty = Dot( my, this.pos );
        var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos ); 
        return [mx[0], my[0], mz[0], 0, mx[1], my[1], mz[1], 0, mx[2], my[2], mz[2], 0, tx, ty, tz, 1]; 
    };
    this.Orbit = function() {
        return Multiply(this.LookAt(), this.OrbitMatrix());
    }; 
    this.Track = function() {
        return Multiply(this.OrbitMatrix(), this.AutoModelMatrix());
    }
    this.OrbitMatrix = function() {
        return (this.mouse_drag || (this.auto_rotate && this.auto_spin)) ? Multiply(this.current_orbit_mat, this.orbit_mat) : this.orbit_mat;
    };
    this.AutoModelMatrix = function() {
        return this.auto_rotate ? Multiply(this.current_model_mat, this.model_mat) : this.model_mat;
    };
    this.Update = function(vp_size) {
        if (vp_size)
            this.vp = vp_size;
        var current_T = this.Time();
        this.current_model_mat = IdentM44()
        if (this.mouse_drag) {
            this.current_orbit_mat = Rotate(IdentM44(), this.mouse_drag_angle, this.mouse_drag_axis);
        } else if (this.auto_rotate) {
            if (this.auto_spin ) {
                if (this.mouse_drag_time > 0 ) {
                    var angle = this.mouse_drag_angle * (current_T - this.rotate_start_T) / this.mouse_drag_time;
                    this.current_orbit_mat = Rotate(IdentM44(), angle, this.mouse_drag_axis);
                }
            } else {
                var auto_angle_x = Fract( (current_T - this.rotate_start_T) / 13000.0 ) * 2.0 * Math.PI;
                var auto_angle_y = Fract( (current_T - this.rotate_start_T) / 17000.0 ) * 2.0 * Math.PI;
                this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_x, 0 );
                this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_y, 1 );
            }
        }
    };
    this.ChangeMotionMode = function(drag, spin, auto ) {
        var new_drag = drag;
        var new_auto = new_drag ? false : auto;
        var new_spin = new_auto ? spin : false;
        change = this.mouse_drag != new_drag || this.auto_rotate != new_auto || this.auto_spin != new_spin; 
        if (!change)
            return;
        if (new_drag && !this.mouse_drag) {
            this.drag_start_T = this.Time();
            this.mouse_drag_angle = 0.0;
            this.mouse_drag_time = 0;
        }
        if (new_auto && !this.auto_rotate)
            this.rotate_start_T = this.Time();
        this.mouse_drag = new_drag; 
        this.auto_rotate = new_auto;  
        this.auto_spin = new_spin;
        this.orbit_mat = Multiply(this.current_orbit_mat, this.orbit_mat);
        this.current_orbit_mat = IdentM44();
        this.model_mat = Multiply(this.current_model_mat, this.model_mat);
        this.current_model_mat = IdentM44();
    };
    this.OnMouseDown = function( event ) {
        var rect = gl.canvas.getBoundingClientRect();
        if ( event.clientX < rect.left || event.clientX > rect.right ) return;
        if ( event.clientY < rect.top || event.clientY > rect.bottom ) return;
        if (event.button == 0) { // left button
            this.mouse_start = [event.clientX, event.clientY]; 
            this.ChangeMotionMode( true, false, false );
        }
    };
    this.OnMouseUp = function( event ) {
        if (event.button == 0) { // left button
            this.ChangeMotionMode( false, true, true );
        } else if (event.button == 1) {// middle button
            this.ChangeMotionMode( false, false, !this.auto_rotate );
        }
    };
    this.OnMouseMove = function( event ) {
        var dx = (event.clientX-this.mouse_start[0]) / this.vp[0];
        var dy = (event.clientY-this.mouse_start[1]) / this.vp[1];
        var len = Math.sqrt(dx*dx + dy*dy);
        if (this.mouse_drag && len > 0) {
            this.mouse_drag_angle = Math.PI*len;
            this.mouse_drag_axis = [dy/len, 0, -dx/len];
            this.mouse_drag_time = this.Time() - this.drag_start_T;
        }
    };

this.domElement = document;
var cam = this;
//this.domElement.addEventListener( 'contextmenu', function(e) { event.preventDefault(); }, false );
this.domElement.addEventListener( 'mousedown', function(e) { cam.OnMouseDown(e) }, false );
this.domElement.addEventListener( 'mouseup', function(e) { cam.OnMouseUp(e) }, false );
this.domElement.addEventListener( 'mousemove', function(e) { cam.OnMouseMove(e) }, false );
//this.domElement.addEventListener( 'mousewheel', hid_events.onMouseWheel, false );
//this.domElement.addEventListener( 'DOMMouseScroll', hid_events.onMouseWheel, false ); // firefox
};

var ShProg = {
Create: function (shaderList) {
    var shaderObjs = [];
    for (var i_sh = 0; i_sh < shaderList.length; ++i_sh) {
        var shderObj = this.Compile(shaderList[i_sh].source, shaderList[i_sh].stage);
        if (shderObj) shaderObjs.push(shderObj);
    }
    var prog = {}
    prog.progObj = this.Link(shaderObjs)
    if (prog.progObj) {
        prog.attrInx = {};
        var noOfAttributes = gl.getProgramParameter(prog.progObj, gl.ACTIVE_ATTRIBUTES);
        for (var i_n = 0; i_n < noOfAttributes; ++i_n) {
            var name = gl.getActiveAttrib(prog.progObj, i_n).name;
            prog.attrInx[name] = gl.getAttribLocation(prog.progObj, name);
        }
        prog.uniLoc = {};
        var noOfUniforms = gl.getProgramParameter(prog.progObj, gl.ACTIVE_UNIFORMS);
        for (var i_n = 0; i_n < noOfUniforms; ++i_n) {
            var name = gl.getActiveUniform(prog.progObj, i_n).name;
            prog.uniLoc[name] = gl.getUniformLocation(prog.progObj, name);
        }
    }
    return prog;
},
AttrI: function (prog, name) { return prog.attrInx[name]; },
UniformL: function (prog, name) { return prog.uniLoc[name]; },
Use: function (prog) { gl.useProgram(prog.progObj); },
SetI1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1i(prog.uniLoc[name], val); },
SetF1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1f(prog.uniLoc[name], val); },
SetF2: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform2fv(prog.uniLoc[name], arr); },
SetF3: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform3fv(prog.uniLoc[name], arr); },
SetF4: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform4fv(prog.uniLoc[name], arr); },
SetM33: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix3fv(prog.uniLoc[name], false, mat); },
SetM44: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix4fv(prog.uniLoc[name], false, mat); },
Compile: function (source, shaderStage) {
    var shaderScript = document.getElementById(source);
    if (shaderScript)
        source = shaderScript.text;
    var shaderObj = gl.createShader(shaderStage);
    gl.shaderSource(shaderObj, source);
    gl.compileShader(shaderObj);
    var status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
    if (!status) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : null;
},
Link: function (shaderObjs) {
    var prog = gl.createProgram();
    for (var i_sh = 0; i_sh < shaderObjs.length; ++i_sh)
        gl.attachShader(prog, shaderObjs[i_sh]);
    gl.linkProgram(prog);
    status = gl.getProgramParameter(prog, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(prog));
    return status ? prog : null;
} };

var VertexBuffer = {
Create: function(attribs, indices, type) {
    var buffer = { buf: [], attr: [], inx: gl.createBuffer(), inxLen: indices.length, primitive_type: type ? type : gl.TRIANGLES };
    for (var i=0; i<attribs.length; ++i) {
        buffer.buf.push(gl.createBuffer());
        buffer.attr.push({ size : attribs[i].attrSize, loc : attribs[i].attrLoc, no_of: attribs[i].data.length/attribs[i].attrSize });
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer.buf[i]);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array( attribs[i].data ), gl.STATIC_DRAW);
    }
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    if ( buffer.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer.inx);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    }
    return buffer;
},
Draw: function(bufObj, attribs) {
    for (var i=0; i<bufObj.buf.length; ++i) {
        if ( attribs && !attribs.includes(i))
            continue;
        gl.bindBuffer(gl.ARRAY_BUFFER, bufObj.buf[i]);
        gl.vertexAttribPointer(bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray( bufObj.attr[i].loc);
    }
    if ( bufObj.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufObj.inx);
        gl.drawElements(bufObj.primitive_type, bufObj.inxLen, gl.UNSIGNED_SHORT, 0);
        gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
    }
    else
        gl.drawArrays(bufObj.primitive_type, 0, bufObj.attr[0].no_of );
    for (var i=0; i<bufObj.buf.length; ++i)
        gl.disableVertexAttribArray(bufObj.attr[i].loc);
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
} };

var FrameBuffer = {};
FrameBuffer.Create = function( vp, texturePlan ) {
    var texPlan = texturePlan ? new Uint8Array( texturePlan ) : null;
    var fb = gl.createFramebuffer();
    var fbsize = Math.max(vp[0], vp[1]);
    fbsize = 1 << 31 - Math.clz32(fbsize); // nearest power of 2
    fb.width = fbsize;
    fb.height = fbsize;
    gl.bindFramebuffer( gl.FRAMEBUFFER, fb );
    fb.color0_texture = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, fb.color0_texture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, fb.width, fb.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, texPlan );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE );
  	gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE );
    fb.renderbuffer = gl.createRenderbuffer();
    gl.bindRenderbuffer( gl.RENDERBUFFER, fb.renderbuffer );
    gl.renderbufferStorage( gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, fb.width, fb.height );
    gl.framebufferTexture2D( gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, fb.color0_texture, 0 );
    gl.framebufferRenderbuffer( gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, fb.renderbuffer );
    gl.bindTexture( gl.TEXTURE_2D, null );
    gl.bindRenderbuffer( gl.RENDERBUFFER, null );
    gl.bindFramebuffer( gl.FRAMEBUFFER, null );

    fb.Bind = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, this );
        if ( clear ) {
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.Release = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, null );
        if ( clear ) {
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.BindTexture = function( textureUnit ) {
        gl.activeTexture( gl.TEXTURE0 + textureUnit );
        gl.bindTexture( gl.TEXTURE_2D, this.color0_texture );
    };

    return fb;
}

initScene();
  
})();
   
</script>

</body>